Anatomy and Histology of the Breast

Question 1

The breast is a subcutaneous organ. What does this tell us about its position?

Answer 1

• It is anterior to the muscles of the body wall

- subcutaneous indicates it is an organ within the skin

Question 2

How is the breast divided?

Answer 2

• 15-25 lobes
• each contain lobules (compound tubulo-acinar glands)
• these drain to the nipple via a series of ducts
• Septa between lobes is made up of dense CT
• Adipose tissue surrounds the dense connective tissue

Question 3

What name is given to the duct belonging to each lobe of the breast?

Answer 3

Lactiferous duct

=> these converge at the nipple

Question 4

What does the word “compound” indicate when describing breast lobules as “compound tubulo-acinar glands”

Answer 4

Indicates that the duct system is branching

Question 5

An expansion occurs in the lactiferous duct as it reaches the nipple. What is this known as?

Answer 5

Lactiferous sinus

Question 6

What other name is given to the dense aggregations of connective tissue causing septa between the lobes of the breast

Answer 6

Suspensory ligaments

• these also act to suspend the breast from either the clavicles or the deep fascia
• more of these ligaments are present in the upper portion of the breast for this purpose

Question 7

What is the basic functional secretory unit in the breast?

Answer 7

Terminal Duct Lobular Unit (TDLU)

Question 8

Explain the flow of secretions from the Terminal Duct Lobular Unit (TDLU) to the nipple?

Answer 8

Terminal ductules

• > intralobular collecting duct
• > lactiferous duct for that lobe

This leads to the nipple, passing through the lactiferous sinus

Question 9

Describe the difference in the type of connective tissue found inside and outside the lobules of the breast?

Answer 9

Dense connective tissue surrounding the lobule (OUTSIDE)

Looser connective surrounding the acini (INSIDE)

Question 10

Why is loose connective tissue found inside the lobules of the breast?

Answer 10

It allows rapid expansion in pregnancy

Question 11

The acini of the lobules are lined by what cells?

Answer 11

• secretory epithelial cells (vary from cuboidal to columnar)
• these are then surrounded by surrounded by myoepithelial cells (contractile)

Question 12

Describe the epithelial lining of larger ducts such as the lactiferous ducts

Answer 12

• varies from thin stratified squamous to stratified cuboidal
• Myoepithelial cells are still present

Question 13

What is the red staining that is present in the lactiferous ducts on histology?

Answer 13

Coagulated proteins being secreted

Question 14

Mammary glands are often seen as a modification of which other existing gland?

Answer 14

Sweat gland

• secretory
• found in the skin (s/c organ)

Question 15

Describe the structure of the nipple

Answer 15

• wrinkled surface
  => thin, highly pigmented keratinized stratified squamous epithelium (EPIDERMIS)
• core of dense irregular connective tissue (DERMIS) with bundles of smooth muscle (NOT usually found in skin)
• Many sebaceous glands open directly onto the surface of the nipple (different to normal skin where this would occur via a hair follicle)

Question 16

Describe how the composition of the breast even changes in pregnancy

Answer 16

FOLLICULAR phase

• cells are shorter and closer together
• lumen of duct systems are difficult to identify

LUTEAL phase

• epithelial cells increase in height
• lumen of the ducts = enlarged and more obvious
• small amounts of secretions appear in the ducts.

Question 17

Describe the dramatic changes that take place during each trimester of pregnancy?

Answer 17

1st Trimester:

• elongation and branching of smaller ducts
• proliferation of epithelial and the myoepithelial cells

2nd Trimester:

• Glandular tissue develops with differentiation of secretory alveoli (acini)
• Plasma cells and lymphocytes infiltrate nearby connective tissue

3rd Trimester:

• Secretory alveoli mature
• Development of extensive rER (for protein production to go into milk)

Question 18

What two types of tissue in the breast tend to reduce in amount when a woman becomes pregnant?

Answer 18

Connective and adipose tissue

Question 19

Describe how a lactating breast can be identified on histology

Answer 19

• secretory alveoli have matured and appear as swollen regions
• only a few adipose cells remain in the septa
• epithelial elements appear more proliferative
• Plasma cells can be identified (large, pink to due rER proteins, clock face nuclei)

Question 20

What is the purpose of plasma cells in the breast tissue?

Answer 20

IgA production to be secreted into colostrum and eventually breast milk

Question 21

Describe the composition of human milk

Answer 21

88% water
1.5% protein (lactalbumin and casein)
7% carbohydrate (mainly lactose)
3.5% lipid

Small quantities of: ions, vitamins and IgA

Question 22

Describe how Lipid droplets are secreted into breast milk?

Answer 22

Apocrine secretion

- Like exocytosis BUT with a membrane and small amount of cytoplasm encompassing the secreted droplet

Question 23

Describe how proteins made in the rER are secreted into the breast milk?

Answer 23

Merocrine secretion (exocytosis)

• Secreted via vesicles (v)
• These merge with the apical membrane to release only their contents into the duct system

Question 24

What other form of secretion is possible from the glands in the breast tissue?

Answer 24

Holocrine Secretion

• involves death of entire cell
• cell fills with sebum droplets
• cell bursts open and expels contents

Question 25

Describe the changes in the breast structure that occur after the menopause?

Answer 25

• secretory cells of TDLU’s degenerate
• leaves only ducts behind
• connective tissue = fewer fibroblasts, collagen and elastic